Wingtips for PW-5
On Jun 10, 6:47*am, kilocharlie kilocharlie.
wrote:
**** .. In a matter of fact, PW-5 is built in the "tradition" of other
polish glass gliders ( Jantar, Acro etc ...) ... strong and
over-engineered at best - LIKE TANK ... don't be fool by the light
"feeling"...
I've lifted the PW5 wing and felt its flex, and I've seen the wing
sandwich plies where one got broken open in a minor landing mishap. I
stand by my assertion that it is a lightly built glider.
Don't get me wrong, I think it is a perfectly safe glider. I am
confident that it is well-engineered, and that it is every bit as
strong as it needs to be to react all of the flight loads within its
operational envelope.
What I think it doesn't have is margin for loads outside the envelope.
Things like ground handling loads, mishaps, minor accidents, and
things of that nature. Margin is what gives gliders robustness and the
ability to operate under harsh conditions and trying circumstances. I
definitely agree that the other Polish gliders you name have such
margin. But that margin has cost, and the cost is extra weight.
To some degree, the lack of margin that I mention is inescapable when
building small, inexpensive gliders. It is inescapable because when
you scale down the size of the glider you generally cannot scale down
the size of the pilot to match.
In order to make the glider climb well, you need it to have low wing
loading. But small gliders have small wings, and the pilots that they
need to carry are generally not any lighter than the pilots of larger
gliders. So to make it climb well, you make it lighter by being more
careful with materials and eliminating margin where practical.
Of course, you can make the glider small, light, and robust by using
very strong high-tech materials like pre-preg carbon like the
SparrowHawk. But then you throw inexpensive right out the window. It's
all a big compromise, and always has been.
Thanks, Bob K.
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